Retractable knife



FIG. 1 is a front perspective view showing my new design for aretractable knife according to the present invention;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a front view thereof;

FIG. 5 is a rear view thereof;

FIG. 6 is a side elevational view thereof opposite to that shown in FIG.2; and,

FIG. 7 is a bottom plan view thereof.

I claim the ornamental design for a retractable knife, as shown anddescribed.